A planetary gearbox is a combination of gears in a state in which sun gears, ring gears and planetary gears are disposed in a concentric line.
In the case of an identical gear ratio, the planetary gearbox has a small volume, a concentric input/output and high power transmission efficiency compared to a gear train disposed in a gearbox that operates based on a different principle and thus is widely used in the field in which small size and lightweight are required.
In the related art, Korean Patent Application No. 10-2005-0132839 discloses a self centering type assembling device for a planetary reduction gear so as to obtain a large gear ratio by applying the planetary gear.
However, in Korean Patent Application No. 10-2005-0132839 that is the related art, a reverse rotational force of an input portion cannot be converted into a forward direction.
In order to solve the conventional problem, Korean Patent No. 1,190,755 discloses a star type forward • reverse one way transmission.
In the transmission disclosed in Korean Patent No. 1,190,755, a forward rotational force transferred through a power transmission unit is transferred to a main carrier using a forward ratchet so that the forward rotational force can be output in a forward direction.
In the transmission disclosed in Korean Patent No. 1,190,755, a reverse rotational force transferred through the power transmission unit is transferred to an internal carrier using a reverse ratchet, and a large output in the forward direction can be obtained while the speed of the carrier is reduced, using a sun gear and a planetary gear engaged with the other side of the internal carrier and a ring gear of an external carrier.
However, in Korean Patent No. 1,190,755 that is the related art has a critical problem that the main carrier cannot move backward.